Navigational computer



Feb. 24, 1970 L. A. WARNER 7,

NAVIGATIONAL COMPUTER Filed May 8, 1968 7 Sheets-Sheet 1 INVENTOR L.OU/S ,4. WARNER ATTO/QNE Y5 Feb. 24, 1970 L. A. WARNER 3,497,678

NAVIGATIONAL COMPUTER Filed May 8, 1968 Q 7 Sheets-Sheet 2 INVENIORLOU/5 14. WARNER fimwwww Feb. 24, 1970 L. A. WARNER 3,497,678

NAVIGATIONAL COMPUTER I Filed May a, 1968 7 Shets-Sheet a mm-vm 02 EINVENTOR LOU/5 A. WARNER QM MM ,4 TTORNE Y5 Feb. 24, 1970 WARNER3,497,678

NAVIGATIONAL COMPUTER Filed May 8, 1968 7 Sheets-Sheet 4 INVENTOR. LOU/S,4. WARNER p wiiymwaww A T TORNE Y5 Feb. 24, 1970 WARNER 3,497,678

NAVIGATIONAL COMPUTER Filed May 8, 1968 7 Sheets-Sheet 5 INVENTOR LOU/SA. WARNER A TTORNE Y5 Feb. 24, 1970 WARNER NAVIGATIONAL COMPUTER 7Sheets-Sheet 6 Filed May 8. 1968 'INVENTOR. LOU/S ,4. WARNER BY 4Arrows/5Y5 Feb. 24, 1970 WARNER 3,497,678

NAVIGATIONAL COMPUTER Filed May 8, 1968 I 7 Sheets-Sheet '7 INVENTOR.LOU/s 4. WARNER A 7'TORNE Y5 United States Patent O 3,497,678NAVIGATIONAL COMPUTER Louis A. Warner, 5223 N. Natoma, Chicago, Ill.60656 Filed May 8, 1968, Ser. No. 727,522 Int. Cl. G06c 1/00, 27/00;G06g 1/00 U.S. Cl. 235-61 11 Claims ABSTRACT OF THE DISCLOSURE componentreference lines, to read and set wind speed components.

This invention relates, in general, to navigational computers and, inparticular, to navigational computers for solving wind vector problems.

In U.S. Patent 2,775,404, there is disclosed a navigational computer forcomputing the speed and direction of the wind while in flight, based oncertain given navigational data, and for computing the magnetic headingand ground speed for planning a flight when the speed and direction ofthe wind is forecast or known. Generally, the computer has a log cosinescale, a log sine scale and a logarithm speed scale on it whichcooperate to perform computations and solutions of wind vector problems.The

air speed and the Wind are resolved into components by performing thenecessary trigonometric computations, on these scales, by the relativepositioning of the discs of the computer. The computer also has agraphical portion which is formed by a circular grid and a rectangulargrid superimposed with one another. The mathematical relationshipbetween these grids and the cooperating log speed scale and the log sineand cosine scales is such as to permit direct reading after an initialsetting is made. The subject patent contains a detailed explanation ofthe theory and the operation of the computer to solve navigational windvector problems.

The computer of the present invention is generally like the computer ofthe U.S. Patent 2,775,404, in that it also has a log cosine scale, a logsine scale and a logarithm speed scale for solving navigational windvector problems. The circular and rectangular grids forming thegraphical portion of the latter computer have been eliminated, however,and replaced with mechanical computer means. These mechanical computermeans are used in cooperation with a pair of straight lines whichperpendicularly intersect one another at the central axis of thecomputer, to permit direct readings to be made, after the computer isinitially set up. Improved log cosine, log sine and numerical log speedscales also are provided so that the computer, while operating on thesame theory as the computer of the subject patent, is far more accurate,is easier to read, and eliminates the need to interpret and/orinterpolate the readings. Other improved features also are provided, aswill be apparent from the description below.

Accordingly, it is an object of the present invention to provideimproved navigational computers, particularly of the type adapted tosolve navigational wind vector problems.

Another object is to provide improved navigational computers of theabove type which have a design such 3,497,678 Patented Feb. 24, 1970that the solutions can be more accurately computed and read.

Still another object is to provide improved navigational computers ofthe above type having mechanical cursor means which are operable toaccurately determine the wind components.

A still further object is to provide improved naviga tional computers ofthe above type which are of a simple, inexpensive construction, yetsturdy, accurate and compact.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The above objectives are accomplished with a navigational computer whichincludes, generally, a base, a pair of intermediate discs, and a topdisc, all aflixed together in a concentric fashion and rotatablerelative to one another. One of the intermediate discs has a log cosinescale and a log sine scale on it which are cooperatively arranged with alogarithm speed scale on the base disc to set or read crab angles,effective true air speeds and wind-speed components. The base disc alsohas a true course index on it which functions with a 360 compass rose onthe other one of the intermediate discs, to set or read true courses andtrue headings. The top disc has a wind direction arrow for setting orreading wind speeds, and a mechanical wind component computing deviceincluding a cursor slider which is slidably aflixed to the top disc anda cursor which is pivotally afi'ixed to the cursor slider, for settingor reading wind components. The cursor slider is cooperatively arrangedwith the wind-speed scale on the top disc and has an index for settingor reading wind speeds on the windspeed scale. The cursor pivotallyaflixed to the cursor slider has a wind-speed component scale on it and,when the wind direction arrow is set in the direction of the wind andthe index on the cursor slider is set over the wind speed on thewind-speed scale on the top disc, the wind components can be read or seton the wind-speed component scale on the cursor, by pivotally moving thelatter so that it extends perpendicular to and over respective ones of apair of reference lines on the base disc, and reading or setting thewind components at the points Where the reference lines intersect thewind-speed component scale on the cursor. In a preferred embodiment, thetop disc is eliminated and only an arm having a wind direction arrow anda reference index is used. The cursor slider, in this case, is slidablyafiixed to and cooperatively arranged with the arm. With thesearrangements of the computer, more accurate readings can be made,directly and without the need of interpreting or interpolating theindicated wind-speed component values.

The invention accordingly comprises an article of manufacture possessingthe features, properties, and the relation of elements which will beexemplified in the article hereinafter described.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a top plan view of a navigational computer exemplary of theinvention;

FIG. '2 is a sectional view of the computer, taken along lines 22 ofFIG. 1;

FIG. 3 is a top plan view of the base disc of the computer of FIG. 1;

FIG. 4 is a top plan view of the intermediate disc of the computer ofFIG. 1 which is positioned atop the base disc;

FIG. 5 is a top plan view of the other one of the intermediate discs,illustrating the 360 compass rose thereon;

FIG. 6 is a top plan view of the top disc of the computer of FIG. 1,illustrating the wind-speed scale formed on it;

FIG. 7 is a 'tOp plan view of the top disc of the computer of FIG. 1,illustrating the mechanical wind component computing device afiixed toit;

FIG. 8 is a similar top plan view of the top disc of the computer,illustrating a mechanical wind component computing device which isexemplary of a second embodiment of the invention affixed to it;

FIG. 9 is a top plan view of the computer, illustrating the manner inwhich the crosswind and tailwind (or headwind) components aredetermined, for an assumed navigational wind-speed problem;

FIG. 10 is a top plan view of the computer, illustrating a modifiedmechanical wind component computing device afiixed to it, and furtherillustrating the manner in which the computer can be used to solve anassumed navigational wind-speed problem using the law of sines; and

FIG. 11 is a similar top plan view of the computer of FIG. 10,illustrating another setting thereof when solving the assumednavigational wind-speed problem.

Similar reference characters refer to similar parts throughout theseveral views of the drawings.

Referring now to the drawings, in FIG. 1 there is illustrated a computer10 having four circular discs 12, 14, 16 and 18 which are affixedtogether, concentrically, atop one another, as illustrated in FIG. 2, bymeans of a grommet 20 and a spring washer 22. Each of the discs 12, 14,16 and 18 is rotatable with respect to the others, as described morefully below. The circular disc 12, is opaque and, as can be best seen inFIG. 3, has two spaced-apart annular rings 24 and 26 thereon, betweenwhich is a logarithmic speed scale 28. The rings 24 and 26 each iscolored so to both color-code and highlight a log cosine scale 32 and alog sine scale 34, respectively, on the disc 14. The speed scale 28 hasan index 30 which, in the illustrated example, is a solid-colored circlehaving the numeral 10 therein.

The disc '14 is of a transparent material and is affixed atop the disc12 (FIG. 2). As can be best seen in FIG. 4, the disc 14 has a diametersubstantially the same as that of the disc 12. The log cosine scale 32and the log sine scale 34 are printed peripherally about the face of thedisc 12, in positions so as to overlay the annular rings 24 and 26,respectively, and have indexes 35 and 36, respectively, which arepositioned directly opposite one another, on each of the opposite sidesof the speed scale 28. As indicated above, the rings 24' and 26 bothcolor-code and highlight the log cosine and the log sine scales so thatthey can be easily observed and read.

While it will be appreciated that a logarithmic scale never reaches thezero value, for the purpose of this computer, the indexes 35 and 36 arelabeled and 90, respectively, and are considered as the origin orstarting point of the log cosine and sine scales 32 and 34.

The log cosine scale 32 extends about the periphery of the disc 12 in acounter-clockwise manner, while the log sine scale 34 extends about thedisc 12 in a clockwise fashion. Also, for all practical purposes, eachof these scales extend from 0 to 90 so that any angle can be readdirectly on either of the two scales, without the need of converting it.

The disc 14 also has a true course index 39, which is labeled TC,positioned such that it lies adjacent and is functionally associatedwith a 360 compass rose 40 formed on the disc 16 (described below). Theindex 39 and the indexes 35 and 36 all are aligned in a fashion suchthat each of them would lie along a radial line extended outwardly fromthe central axis (defined by the grommet 20) of the computer 10, to itsouter edge, for reasons set forth below. A scale 38 which is graduatedfrom 0 to 90 and then from 90 to 0, in both a clockwise and a co te-clockwise direction from the true course index 39 also is provided onthe disc 14, for determining drift corrections and relative wind angles,in a manner described below.

Straight reference lines 41 and 42 are provided on the disc 14, andfunction in conjunction with a wind-speed component scale 60 (describedbelow) to set or read windspeed components. These reference lines 41 and42 are of equal length and perpendicularly intersect one another, attheir midpoints, at the central axis of computer 10. The refernce lines41 and 42 also are positioned so that one of them, in the illustratedexample, reference line 41, is aligned with and extends inwardly fromthe index 39.

Indicia is printed on the face on the disc 14 for indicating, forexample, whether the computed wind components are right or leftcrosswinds, and head or tailwinds.

The disc 16 (FIG. 5) also is transparent and, as can be seen in FIG. 2,is affixed atop the disc 14. The diameter of the disc 16 preferablysubstantially corresponds to the smaller diameter of the annular ring26, that is, its diameter at the inside edge thereof, and the 360compass rose is printed on the outer marginal edge thereof.

The disc 18 (FIG. 6) likewise is of a transparent material and, in FIG.2, it can be seen that it is aflixed atop the disc 16. The disc 18 has adiameter such that its peripheral edge extends adjacent the compass rose40 of the disc 16. A pair of spaced-apart, parallel elongated slots 44and 45 are formed in the disc 18, at equal spaced distances on theopposite sides of the central axis of the computer 10, respectively. Awind direction arrow 46 extends diametrically across the disc 18,between the slots 44 and 45. This wind direction arrow 46 advantageouslyis dfined by a solid shaft portion 47 extending from the central axisoutward to the edge of the disc 18 Where it terminates with an arrowhead48 and a pair of parallel lines 49 and 50 extending in the oppositedirection from the central axis to the edge of the disc 18 Where itterminates with a tail 53. A wind-speed scale 51 is provided on the disc18, and is cooperatively arranged with the wind direction arrow 46. TheWindspeed scale 51 has indicia in the form of straight lines which areextended transversely across the shaft portion 47 and which are numberedin tens, in increasing value from 0 knots at the tip of the arrowhead 48to 50 knots at the central axis of the computer 10.

As can be best seen in FIG. 7, a wind-speed component computing device52 is aifixed to the disc 16, and includes a cursor slider 54, Thecursor slider 54 has a pair of outwardly extending flanges (not shown)which are reveresely folded so as to extend through respective ones ofthe slots 44 and 45 to slidably secure the cursor slider 54 and hencethe computing device 52 to the disc 18. The cursor slider 54 has anindex 59 on it, which index is a line extending transversely across itand positioned so as to cooperate with the windspeed scale 51. The index59 is aligned with the indicia of the wind-speed scale 51, to apply awind-speed value to the computer 10, as described more fully below.

The cursor 56 is generally triangular-shaped and is pivotally affixed tothe cursor slider 54, by means of a grommet 62. The wind-speed componentscales 60 and 61 which are like the Wind-speed scale 51 are provided onthe cursor 56, and extend perpendicular to one another. The wind-speedcomponent scales 60, 61 increase from 0 knots at the grommet 62 to 50knots at their outer ends. The cursor 56 is affixed to the cursor slider54 in a fashion such that the indicia of the wind-speed scale 51 and thewind-speed component scales 60 and 61 increase in value in oppositedirections.

Having now described the construction of the computer 10, its operationin solving an air navigational problem can be described as follows. Theproblem or solution which is most often encountered is to determine thetrue heading, the crab angle, and the ground speed while planning aflight, when the true course, the true air speed, the forecast winddirection and wind speed are known. Assuming that:

the computer is manipulated in the manner described below to determinethe true heading, the crab angle and the ground speed.

The disc 14 is first rotated with respect to the disc 12, to align theindexes 35 and 36 with the indicia corresponding to 240 knots (the trueair speed) on the air speed scale 28, as illustrated in FIG. 1, Next,the disc 16 is rotated with respect to one another, to align the truecourse index 39 with the indicia corresponding to 050 (the true course)on the compass rose 40. Holding the discs 12, 14 and 16 fixed withrespect to one another, the disc 18 is rotated to set the tail 53 of thewind direction arrow 46 to the direction from which the wind blows, thatis, in this case, with the indicia corresponding to 200 (the assumedwind direction) on the compass rose 40. With this arrangement, the winddirection arrow 46 presents an actual picture of how the wind blows withrespect to the aircraft so that the problem can be more easilyvisualized and solved. The cursor slider 54 is slidably moved to alignthe index 59 thereon over the indicia corresponding to knots (the windspeed) on the wind-speed scale 51.

After these initial settings have been made, the crosswind componentsare easily, quickly and accurately determined as follows. The cursor 56is pivotally moved so that the wind-speed component scales 60 and 61thereon extend perpendicular to and over respective ones of thereference lines 41 and 42, as illustrated in FIG. 1. A crosswindcomponent of 8 knots is read on the windspeed component scale 61, wherethe reference line 41 intersects it. The crosswind is determined to be aright crosswind, by noting the position of the grommet 62, that is,whether it is positioned to the right or to the left of the referenceline 41, and the legend of the disc 12, which, in this case, reads rightcrosswind. Accordingly, the crosswind component is determined to be aright crosswind of 8 knots.

The value 8 knots is now located on the logarithmic air-speed scale 28(or, in this case, 80 knots since the indicia 80 can be interpreted as8.0 or 80 or 800 etc., as in the case of any slide rule) and below itjust to the left on the log sine scale 34 the value of approximately 8is read. The 2 is the crab angle and, since it is a right crosswind, thecrab angle is added to the true course of 050 and the true heading istherefore determined to be 052.

The headwind or tailwind component, as the case may be, is determined byreading the value 14 knot on the wind-speed component scale 60, over thereference line 42, and it is further noted from the position of thegrommet 62 and the legend on the disc 12 that this wind component is atailwind.

Ground speed is determined by adding the tailwind to, or substracting aheadwind from, the consine component of the true airspeed. The cosinecomponent of the true airspeed, in this case, is determined by observingthe air speed which is aligned with the angle 2 on the log cosine scale32. For all practical purposes, this value is read as 240 knots,although it is actually slightly less than this. The tailwind of 14knots is added to this 240 knots, and the ground speed therefore is 254knots.

From the above description, it is seen that the crosswind components areeasily and quickly determined and, furthermore, that they can be readdirectly from the windspeed component scales 60 and 61 without the needto interpret the indicated readings, by extending them to intersectanother scale or to interpolate the reading on this other scale. 'It isfurther apparent that the indicated readings are far more accurate sincethe wind direction and wind speed both are precisely applied to thecomputer 10 and the wind-speed components are read directly from thewind-speed component scales 60 and 61 as described above. Furthermore,the computer 10 is extremely accurate at low wind speeds, whereas othersimilar computers, particularly the computer disclosed in theabove-mentioned US. Patent 2,775,404 are not.

In FIG. 9 the computer 10 is illustrated in the manner in which it isinitially set up to determine another navigational wind-speed problem.In this case, the known elements are:

True course 330 True air speed knots 210 Wind direction 265 Wind speedknots 15 and again it is desired to determine the true heading, the crabangle and the ground speed.

In FIG. 9 it can be seen that the indexes 35 and 36 of the log cosinescale 32 and log sine scale 34, respectively, are aligned with the trueair speed of 210 knots on the logarithmic speed scale 28. The truecourse of 330 on the compass rose 40 is aligned with the true courseindex 39 on the disc 14. The tail 53 of the wind direction arrow 46 isaligned with the wind direction of 265 on the compass rose 40, and thecursor slider 54 is positioned to align its index 59 over the wind speedof 15 knots on the wind-speed scale 51.

The cursor 56 is positioned so that the wind speed component scales 60and 61 extend perpendicular to and over the reference lines 41 and 42,as described above. A headwind component of 7 knots is read on thewindspeed component scale 60, over the reference line 42, and a leftcrosswind of 13 knots is read on the windspeed component scale 61, overthe reference line 41. By following the steps outlined above, the crabangle is determined to be approximately 3.5 and the true headingtherefore is 326.5". The ground speed is determined to be 203 knots.

Another navigational wind-speed problem sometimes encountered is todetermine the wind direction and the wind speed, while in flight, whenthe true course, the true air speed, the true heading and crab angle,and the ground speed are known. To illustrate how the computer 10 ismanipulated to determine the wind direction and speed, assume that theaircraft has the following:

True course 330 True air speed "knots" 210 True head 326.5 Crab angle do3.5 Ground speed knots 203 To solve this problem, the true air speed of210' knots on the logarithmic air-speed scale 28 is aligned with theindex 35 of the log cosine scale 32, and the true course of 330 on thecompass rose 40 is aligned with the true course 39, as illustrated inFIG. 9'.

The headwind component is first determined by multiplying the true airspeed by the cosine of the crab angle, and then subtracting the groundspeed from the determined value. Thus, under 3.5 on the log cosine scale32, the value of 210 knots is read on the speed scale 28. This is thecosine ground speed component and since it is more than the groundspeed, it is apparent that the wind is a headwind. Thus, by subtractingthe ground speed of 203 knots from the cosine ground-speed component of210 knots, the headwind component is found to be 7 knots.

Multiplying the true air speed of 210 knots by the sine of the crabangle of 3.5, the crosswind component is found to be 13 knots. Since thecrab angle is to the left, the wind is obviously a left crosswind.

With these two values determined, two legs of the wind component righttriangle relative to the true course are now known. The wind directionand speed is determined by applying these two values to the wind-speedcomponent computing device 52, as follows: the cursor 56 is positionedso that the wind speed component scales 60 and 61 extend perpendicularto and over the reference lines 41 and 42. The cursor slider 54 issimultaneously moved to align the left crosswind component of 13 knotson the wind-speed component scale 61 over the reference line 41, then isextended perpendicular to and over the reference line 42. The disc 18 isrotated and the position of the cursor 56 is adjusted while it isrotated to align the headwind of 7 knots on the wind-speed componentscale 60 over the reference line 42. In this position, the tail 53 ofthe wind direction arrow 46 is aligned with the wind direction which, inFIG. 9, can be seen to be 265. The index 59 on the cursor slider 54 alsois aligned over the wind speed on the wind-speed scale 51, and the windspeed can be seen to be 15 knots.

In FIG. 8, the disc 16 is illustrated having a windspeed componentcomputing device 70 afiixed to it, which includes a cursor slider 71 anda cursor 72. The cursor slider 71 is identical to the cursor slider 54,and is slidably affixed to the disc 16 in a like fashion. The cursor 71,in this case, however, comprises an elongated, generallyrectangular-shaped member 73 which is pivotally afiixed to the cursorslider 71, by means of a grommet 74. The cursor slider 72 also only hasone wind-speed component scale 75 provided on it, which increases fromknots at the grommet 74 to 50 knots at its outer end. The wind-speedcomponent scale 75 provided on it, which increases from 0 knots at thegrommet 74 to 50 knots at its outer end. The wind-speed component scale75 and the wind-speed scale 51 on the disc 18, therefore increase invalue in opposite directions, in the same fashion as the wind-speedcomponent scales 60 and 61, when the cursor 72 is affixed to the cursorslider 71.

In using the wind-speed component computing device 70 to solve an airnavigational problem, for example, the navigational problem illustratedin FIG. 1, the discs 12, 14, 16 and 18 are initially set-up in the samemanner as described above, when using a computer having a wind-speedcomponent computing device 52 affixed to it.

After these initial settings have been made, however, the cursor 72 ispivotally moved so that it extends perpendicular to and over thereference line 41. A crosswind component of 8 knots is read on thewind-speed component scale 75, where the reference line 41 intersectsit. Next, the cursor 72 is pivotally moved so that it extendsperpendicular to the other reference line 42. A tailwind of 14 knots isread on the wind-speed component scale 75, where the reference line 42intersects it.

It can be seen from the above description that the only major differencein the operation of the computer 10 having a cursor 72 affixed to itinstead of a cursor 56, is that the cursor 72 must be manipulated so asto position it perpendicular to each of the two reference lines 41 and42 in order to determine both crosswind components. In the case of thecursor 56, both crosswind components can be determined with only onesetting.

In FIGS. 10 and 11, the disc 18 and the wind-speed component computingdevice have been substantially modified so as to provide a still moresimplified arrangement. It can be seen that the disc 18 is reduced tomerely a generally rectangular-shaped arm 80 which is rotatably afiixedto and extends diametrically across the disc 16. The end portions ateach of the opposite ends of the arm 80 are formed so as to provide stopshoulders 81 and 82, and all of the indicia except for the winddirection arrow 46 has been removed. A single index in the form of astraight line 83 extends across the width of the arm 80 perpendicular tothe wind direction arrow 46, at the center of the computer.

The wind-speed component computing device 84, in this case, includes acursor slider 85 and a cursor 86. The cursor slider 85 is generallyrectangular-shaped and has a securing and alignment flange 87 and 88integrally formed along each of its opposite sides which are folded overand about the parallel side edges 89 and 90 of the arm 80, to slidablyaffix the cursor slider to the arm. These flanges also abut the stopshoulders 81 and 82 on the arm 80, so that the cursor slider 85 cannotbecome disengaged from the arm.

The cursor 86 comprises an elongated, generally rectangular-shapedmember which is pivotally afiixed to the cursor slider 85, by means of agrommet 91. A single wind-speed scale 92 is provided on the cursor 86,and this wind-speed scale increases from 0 knots at the grommet 91 to 50knots at its opposite end. This wind-speed scale 92 functions both toset the wind speed and to determine wind-speed components, in a mannerdescribed more fully below.

In using this computer to solve an air navigational problem, such as thenavigational problem illustrated in FIG. 1, the discs 12, 14 and 16 areinitially set-up in the same manner as described above. The arm isrotatably adjusted to align the wind direction arrow 46 in the directionthat the wind blows, as illustrated in FIG. 10. The wind speed is set byslidably adjustably positioning the cursor slider and the cursor 86 toalign the indicia on the wind-speed scale 92 corresponding to the windspeed, in this case, 15 knots, over the index 83 on the arm 80.

The crosswind component is determined by pivotally moving the cursor 86so that it extends perpendicular to and over the reference line 41. Inthis position, the value 8 knots is read on the wind-speed scale 92,where the reference line 41 intersects it. Next, the cursor is pivotallymoved so that it extends perpendicular to and over the other referenceline 42. A tailwind of 14 knots is now read on the Wind-speed scale 92,where the reference line 42 intersects it.

It can be seen that the wind-speed components are determined ingenerally the same manner with the cursor 86 as they are with the cursor72. The major advantage and the most desirable features of the lastdescribed arrangement is the simplicity of the arrangement and thesubstantially uncluttered appearance of the computing device, due to theelimination of the wind-speed component scales. This arrangement,accordingly, is generally preferred.

The computer 10 has another feature which is not provided by othersimilar computers. It may be noted that the arrangement of the scales issuch that the computer can be used to easily and quickly solve windvector problems using the right triangle solution rather thangraphically, as described above. This feature is particularly usefulwhen high wind speeds are encountered as, for example, when followingthe jet streams. Such wind vector problems can be graphically solved, inthe manner described above, however, the accuracy of the computers isnot as great.

As an example, suppose that (1) true course is 060,

(2) true airspeed is 360 knots,

(3) the wind direction is 25 0, and (4) the wind speed is 132 knots.

In solving this wind vector problem, the 0 index 35 and the index 36first are aligned with the indicia on the speed scale 28 correspondingto the wind speed which, in this case, is 132 knots, as can be best seenin FIG. 10. The indicia 060 (which is the true course) of the compassrose 40 on the disc 16 is aligned with the true course index 39 (FIG.10), and the tail of the wind direction arrow 46 is aligned with theindicia 250 of the compass rose 40.

After these settings have been made, reference is made to the sacle 38and the wind direction arrow 46 to determine the relative wind angle. Inthis case, it can be seen to be 10. The course component of the wind isnow determined by reading knots on the speed scale 28, below and alignedwith the indicia 10 on the cosine scale 32. .By looking at the directionin which the wind direction arrow 46 points, it can be seen that this isa tailwind. The crosswind component is determined by reading 23 knots onthe speed scale 28, over and aligned with the indicia 10 on the sinescale 34. Again, noting the direction of the wind direction arrow 46, itcan be seen that this is a left crosswind.

Now, the and the 90 indexes 35 and 36 are aligned With the indicia onthe speed scale 28 corresponding to the'itrue airspeed which, in thiscase, is 360 knots, as illustrated in FIG. 11. Knowing the crosswindcomponent is 23 knots, the crab angle is determined by reading the value3 /2" on the sine scale 34, below and substantially aligned with the 23on the speed scale 28. A rule of thumb to follow in determining the crabangle is to use the small angles if the crosswind component is less than1 of the true airspeed. Applying this rule in the instant case, of thetrue airspeed would be 36 knots and the cross wind component is only 23knots, hence the small angle 3 /2 rather than 40 is used. The trueheading is determined by subtracting the crab angle 3 /2 from the truecourse of 0.50", since the wind is a left crosswind. The true headingtherefore is 056.5

The ground speed is determined by, in this case, adding the coursecomponent to the product of the cosine of the crab angle times the trueairspeed since it is a tailwind. The product of the cosine of the crabangle times the true airspeed is determined by reading the valueindicated on the airspeed scale 28, below and aligned with the angle 3/2" on the cosine scale 32. In this case, for all practical purposes, itcan be seen that this value is just slightly less than 360 knots. Addingthe tailwind of 130 knots to this, it is determined that the groundspeed is 490 knots.

From the above description, it can be seen that the wind speedcomponents, the crab angle, the true heading and the ground speed allcan be easily, quickly and accurately determined, regardless of the windspeed.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efiiciently attained and,since certain changes may be made in the above article without departingfrom the scope of the invention, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

Now that the invention has been described, what is claimed as new anddesired to be secured by Letters Patent is:

1. A computer for the solution of navigation problems comprising aplurality of cooperating discs mounted on a common central axis androtatable with respect to each other; a first one of said discs having atrue course index and wind-speed component reference means thereon; asecond one of said discs having a compass rose circumferentially formedon it; said true course index and said compass rose being cooperativelypositioned with respect to one another to set and read true courses onsaid compass rose; and means rotatably affixed to said computer havingthereon a wind direction arrow, a reference index, at least onewind-speed scale, and a mechanical windspeed component computing device,said wind direction arrow being positioned to cooperate with saidcompass rose to set and read wind directions on said compass rose, saidmechanical wind-speed component computing device being operable to setand to read wind speeds on said wind-speed scale and to set and readlongitudinal and transverse wind-speed components on said windspeedscale in cooperation with said windspeed component reference means.

2. The computer of claim 1, wherein said means comprises a third dischaving said wind direction arrow and said wind speed scale provided onit, said mechanical wind-speed component computing device being affixedto said third disc and having said reference index and a wind-speedcomponent scale provided on it, said device being operable to set and toread wind speeds on said wind-speed scale and to set and readlongitudinal and transverse wind-speed components on said wind-speedscale in cooperation with said wind-speed component reference means.

3. The computer of claim 2 wherein said wind-speed component referencemeans comprises a pair of straight lines which perpendicularly intersectone another at said common central axis, one of said lines being alignedwith said true course index on said first disc.

4. The computer of claim 2, wherein said mechanical wind-speed componentcomputing device comprises a cursor slider having said reference indexthereon slidably afiixed to said disc with said reference indexpositioned to cooperate-with said wind-speed scale to set and to readwind speeds thereon, and a cursor having one wind-speed component scalethereon pivotally affixed to said cursor slider, said cursor beingpivotally adjusted to extend perpendicular to and over said pair ofstraight line wind-speed component reference means to set and read saidlongitudinal wind-speed component and said transverse wind-speedcomponent, respectively.

5. The computer of claim 2, wherein said mechanical wind-speed componentcomputing device comprises a cursor slider having said reference indexthereon slidably affixed to said disc with said reference index thereonpositioned to cooperate with said wind-speed scale to set and to readwind speeds thereon, and a cursor having two wind-speed component scalesthereon which have a common index and which are perpendicularly disposedwith respect to one another, said cursor being pivotally aflixed to saidcursor slider and being pivotally positionally adjustable to positioneach of said two wind-speed component scales perpendicular to andextending over different ones of said pair of straight line wind-speedcomponent reference means to simultaneously set and to read both saidlongitudinal and transverse wind-speed components.

6. The computer of claim 1, wherein said means comprises a generallyrectangular-shaped arm rotatably affixed atop the second one of saiddiscs and having said wind direction arrow and said reference indexprovided on it, said mechanical wind-speed component computing devicecomprising a cursor slider slidably aflixed to said arm and a cursorhaving said wind speed scale thereon pvotally aflixed to said cursorslider.

7. The computer of claim 1, further including a disc having alogarithmic numerical air-speed scale thereon; and a disc havinglogarithmic trigonometric function scales thereon; said logarithmicnumerical air-speed scale and said trigonometric function scales beingpositioned to cooperate in slide rule fashion to resolve knownnavigational data into certain trigonometric components.

8. The computer of claim 7 wherein said logarithmic numerical air-speedscale is formed on a fourth disc which is mounted on said common centralaxis and is rotatable with respect to said plurality of cooperatingdiscs; and wherein said logarithmic trigonometric function scales areformed on said first one of said discs.

9. The computer of claim 8 wherein said logarithmic numerical air-speedscale and said trigonometric function scales each have an index whichare aligned.

10. The computer of claim 9 wherein said logarithmic trigonometricfunction scales comprises a cosine and a sine scale in spaced relationon opposite sides of said logarithmic numerical air-speed scale,respectively, said cosine scale including indicia having 0 representedat said index and increasing angles represented about the circumferenceof said disc in a counter-clockwise fashion, said sine scale includingindicia having represented at said index and decreasing anglesrepresented about the circumference of said disc in a counter-clockwisefashion.

1 l 1 2 11. The computer of claim 5, wherein said wind-speed 1,969,9398/ 1934 Nelson 33-76 scale has indicia which increases in value from theouter 2,019,708 11/ 1935 Jones 3376 periphery of said disc toward saidcommon central axis, 2,438,730 3/1948 Watter 3376'X and wherein saidwind-speed component scales on said 2,446,433 8/1948 Putnam 235-61 Xcursor increase in value from said common index toward 5 3,231,188 1/1966 Warner 23561 the outer extremity of said cursor.

RICHARD B. WILKINSON, Primary Examiner References C'ted STANLEY A. WAL,Assistant Examiner UNITED STATES PATENTS 1,910,093 5/1933 Colvin 235-6l1O U.S. Cl. X.R. 1,949,946 3/1934 Viehmann 2356l 33-76; 23578

